Circadian rhythms in Megachile rotundata (Fabricius) PublicDeposited

Descriptions

The rhythms of emergence, oxygen consumption, and activity
were studied in Megachile rotundata with the object of comparing the
results to the major properties of the biological clock such as temperature
independence, susceptibility to light synchronization, and
entrainment. A further objective was to compare the three rhythms
to determine if they were three aspects of the same rhythm or if
they were indeed three different rhythms.
The emergence rhythm proved to possess a period of 23.7 h
in DD and 23.0 h in LL. This difference was not statistically significant.
The emergence period displayed a Q₁₀ of 1.02 for a temperature
rise of 25 to 30° C and a Q₁₀ of 1.12 for a 30 to 35° C temperature
rise. The rhythm was largely refractive to light but very
responsive to temperature from the dark-eyed pupa stage through the
adult stage. The temperature phase response curve displayed phase
advances during the subjective high temperature period and phase delays during the subjective low temperature period. No transients
occurred in the response of M. rotundata to a temperature pulse.
The oxygen consumption rhythm responded to light and temperature
in a manner similar to that of the emergence rhythms.
However, no difference was detected in the length of the oxygen
consumption period in LL as compared to DD. The rhythm did not
respond to light entrainment (LD 12:12). The temperature phase response
curve was similar to that of the emergence rhythm. The
oxygen consumption rhythm was analyzed in the pre-adult and adult
stages using power spectra analyses. The rhythm spectrum appeared
to be less stable in the pre-adult stages than in the adult
stage. The circadian component was very prominent in the adult
while from two to four ultradian components appeared in the pre-adult
stages.
The activity rhythm proved to be very similar to both the
emergence and oxygen consumption rhythms in its response to light
and temperature. Again the response to light was very slight and
was only detected in the period length in LL compared to the period
length in DD. In LL the activity period length was 22.34 h while in
DD the period length was 22.86 h. This difference of 0.52 h was
significant at the five percent level. The temperature response
curve was almost identical to that of the emergence and oxygen consumption
response curves. A comparison of the three rhythms is drawn with the conclusion
that the emergence and activity rhythms are probably the same
basic rhythm. It is possible that the oxygen consumption rhythm is
different from the other two but more experimentation is required before
a more positive conclusion can be made.